The effects of ensiling on dry-matter intake and milk production by lactating dairy cattle given forage as the sole feed
Keady, T.W.J.; Murphy, J.J.; Harrington, D.
Grass and Forage Science 51(2): 131-141
ISSN/ISBN: 0142-5242 DOI: 10.1111/j.1365-2494.1996.tb02047.x
An experiment involving forty-five British Friesian cows in mid-late lactation was carried out to evaluate the effects of ensiling on herbage digestibility, dry-matter intake and milk production. The herbage from the primary growth of a predominantly perennial ryegrass sward that had received 123 kg N ha-1 was zero grazed (ZG) from 27 April to 24 May 1992. Before going onto the experimental diets all animals were offered a common silage as the sole diet and dry-matter intakes and milk yields were recorded. The herbage was mown, picked-up with a precision-chop harvester and offered as the sole diet, twice daily, to fifteen cows that were on average 176 days into lactation. On May 20 herbage from the same sward was harvested identically to the ZG herbage and ensiled, alternative loads being untreated (UT) or treated with formic acid (2.41 t-1) (FA). For silages UT and FA respectively, pH values were 3-94 and 3.92 and ammonia nitrogen concentrations were 95 and 75 (g(kg total N-1)). Forty-two days after ensiling, the silages were fed twice daily as the sole diet to thirty cows which were on average 166 days into lactation. The feeding interval was 28 days and the last 7 days was die main recording period for each treatment. For diets ZG, UT and FA, dry-matter intakes (DMI) (kg d-1), milk yields (kg d-1), fat plus protein yields (kg d-1), milk fat concentration (g kg-1),milk protein concentration (g kg-1) and fat plus protein yields (kg (kg DMI)-1) were 12.70, 11.51 and 12.07 (Av s.e.d.=O.458); 12.79, 10.01 and 10.18 (Av s.e.d.=O.346); 0.900, 0-649 and 0.682 (Av s.e.d. = 0.026); 39-8, 33.7 and 36.7 (Av s.e.d.=O.174); 32.9, 29.9 and 30.0 (Av s.e.d.=O.83); 0.073, 0.055 and 0.055 (Av s.e.d. = 0.003). UT treatment significantly increased dry matter (DM), organic matter (OM), energy and crude fibre digestibilities and the digestible OM concentration. UT and FA compared with ZG altered rumen fermentation patterns, significantly decreasing butyrate and increasing valerate concentrations. FA treatment significantly decreased the non-glucogenic ratio. It is concluded that ensiling using formic acid had no effect on forage DMI relative to the parent fresh herbage. Ensiling either untreated or with formic acid significantly decreased milk yield and milk fat plus protein yield, resulting in a lower efficiency of conversion of DMI to milk fat plus protein.